In the oil and gas industry, modeling of the subsurface is typically utilized for visualization and to assist with analyzing the subsurface volume for potential locations for hydrocarbon resources. Accordingly, various methods exist for estimating the geophysical properties of the subsurface volume (e.g., information in the model domain) by analyzing the recorded measurements from receivers (e.g., information in the data domain) provided that these measured data travel from a source, then penetrate the subsurface volume represented by a subsurface model in model domain, and eventually arrive at the receivers. The measured data carries some information of the geophysical properties that may be utilized to generate the subsurface model.
It is often useful to extract horizons from the seismic data. Horizon extraction in seismic data typically involves of identifying the locations of reflection events where an interface exists. These horizons may be extracted via peaks and or trends from the seismic data as these provide information about the geology that created the seismic response. For example, the ridge curves in 2-D, or ridge surfaces in 3-D, can be used to determine horizons (e.g., curves in 2-D data or surfaces in 3-D data) that correspond to peaks, troughs or zero-crossings of seismic attribute data like amplitude. Similarly, the interpretation of seismic data often involves the estimation of “trends.” These are typically extracted manually by an interpreter to provide a visual aid, but noise and poor imaging require choices to be made (e.g., interpretation of the data) which introduces uncertainty into the process.
To address this concern, several methods exist to automate this process. For example, some methods use local trace correlations to grow a surface from initial (seed) locations. As an example, some software packages provide automatic horizon tracker that is based on a waveform tracking algorithm. See, e.g., Paradigm™ 3D Propagator™ (available at Paradigm's website on Dec. 20, 2012; URL included in the originally filed specification) and dGB's OpendTect (available at Opendtect's website on Dec. 20, 2012; URL included in the originally filed specification). While this technique is useful, it only addresses the issue of creating a single horizon at a time. In particular, horizons from earlier interpretations are merely visual aids and are not further used by this approach to enhance the process to define new horizons. Therefore, it becomes difficult to track multiple horizons and the inconsistencies that often arise.
Another example is a method that conformally defines a horizon based on existing horizons. See, e.g., Origin of gOcad (available at Gocad's website on Oct. 18, 2012; URL included in the originally filed specification). The new horizon is an interpolated surface between a top and a base horizon. As such, the interpolation uses the same parameter throughout the surface. This approach does relies upon an interpolation parameter in one location, which may not be adequate in another location on the horizon.
As the recovery of natural resources, such as hydrocarbons rely, in part, on a subsurface model, a need exists to enhance subsurface models of one or more geophysical properties. In particular, a need exists to enhance the horizon extraction process.